1. Field of the Invention
The present invention relates to a method of manufacturing a quartz double crucible assembly which is utilized for producing silicon crystalline rods.
2. Prior Art
Extensively used for manufacturing silicon monocrystal rods is a Czochralski method which comprises the step of pulling a silicon monocrystal rod from a melt in a crucible while continuously adding a silicon material to the melt in order to maintain the quantity of the melt constant.
FIG. 1 shows an example of a double crucible utilized in such method which includes an outer crucible 100 and a cylindrical inner crucible member 102 housed within the outer crucible 100 so as to be coaxial therewith. The inner crucible member 102 includes a pair of cut-outs 104 and 104 formed at a lower end thereof, and a pipe 106 for feeding a silicon material is disposed with its one end directed toward a space defined between the inner crucible member 102 and the outer crucible 100, whereby the silicon material can be continuously introduced into the space. Thus, by virtue of the provision of the inner crucible member 102, the disturbance produced in the surface of the melt when the silicon material drops into the melt is prevented from being transmitted to a growing portion of a silicon crystalline rod 108, so that the disorder in its crystal structure is positively prevented.
Heretofore, a double crucible as described above has been manufactured by welding the inner crucible member 102 to the outer crucible 100 by hand by using an oxyhydrogen flame burner or the like. However, much time and labor have been required in the welding work, and therefore the manufacturing cost has been increased unduly. Particularly, the problem of increased cost has become more serious with the recent tendency of the diameter of the crucible increasing in size.